Tantalum amido-complexes with chelate ligands useful for CVD and ALD of TaN and Ta205 thin films

ABSTRACT

Tantalum compounds of Formula I hereof are disclosed, having utility as precursors for forming tantalum-containing films such as barrier layers. The tantalum compounds of Formula I may be deposited by CVD or ALD for forming semiconductor device structures including a dielectric layer, a barrier layer on the dielectric layer, and a copper metallization on the barrier layer, wherein the barrier layer includes a Ta-containing layer and sufficient carbon so that the Ta-containing layer is amorphous. According to one embodiment, the semiconductor device structure is fabricated by depositing the Ta-containing barrier layer, via CVD or ALD, from a precursor including the tantalum compound of Formula I hereof at a temperature below about 400° C. in a reducing or inert atmosphere, e.g., a gas or plasma optionally containing a reducing agent.

CROSS-REFERENCE TO RELATED APPLICATION

This is a divisional under 35 USC 120 of U.S. patent application Ser. No. 12/013,433 filed Jan. 12, 2008 in the names of Tianniu Chen, et al. for “TANTALUM AMIDO-COMPLEXES WITH CHELATE LIGANDS USEFUL FOR CVD AND ALD OF TaN AND Ta₂0₅,” now U.S. Pat. No. 7,750,173 issued Jul. 6, 2010, which in turn claims the benefit of priority under 35 USC 119 of U.S. Provisional Patent Application 60/885,459 filed Jan. 18, 2007 in the names of Tianniu Chen, et al. for “TANTALUM AMIDO-COMPLEXES WITH CHELATE LIGANDS USEFUL FOR CVD AND ALD OF TaN AND Ta₂0₅.” The disclosures of said U.S. Pat. No. 7,750,173 and said U.S. Provisional Patent Application 60/885,459 are hereby incorporated herein by reference, in their respective entireties, for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to precursor compositions that are useful for forming tantalum-containing films, e.g., by chemical vapor deposition (CVD) or atomic layer deposition (ALD), as well as to tantalum-containing barrier layers or films and to copper-metallized semiconductor device structures including tantalum-containing layers or films.

2. Description of the Related Art

In the field of semiconductor manufacturing, copper (Cu) and low k dielectrics are being increasingly employed in high performance silicon integrated circuits. Since Cu is very mobile in silicon (Si) and silicon dioxide (SiO₂), effective diffusion barriers against Cu migration are required for the use of Cu metallization, inasmuch as the copper/interlayer dielectric interface determines the stability and reliability of the metallization scheme.

A variety of refractory metals, refractory metal nitrides, and metal-silicon-nitrogen compounds have been intensively investigated for use as barrier material. See, for example, U.S. Pat. No. 6,951,804 to Seutter et al. and U.S. Pat. No. 6,960,675 to Chen et al. Each of these U.S. patents is incorporated herein by reference in their entirety.

Among such materials, tantalum (Ta) and tantalum nitrides (TaN) are considered to be among the most promising candidates because of their stability under high temperature, high degree of adhesion, low resistivity, uniformity of their films and their inertness towards Cu.

As the size of the pattern shrinks and the aspect ratio increases, vapor deposition techniques, e.g., chemical vapor deposition (CVD), atomic layer deposition (ALD), digital CVD, pulsed CVD, or the like, are necessary to deposit the barrier layer, in order to minimize barrier layer thickness while achieving effective barrier properties.

Against this background of continuous shrinkage in feature size and progressive increase in aspect ratio, chemical vapor deposition (CVD) and atomic layer deposition (ALD) are increasingly preferred for depositing thin, conformal and smooth barrier layers in vias and trenches. For such applications, suitable tantalum precursors are required for forming tantalum-containing barrier material on substrates.

From a practical standpoint, Ta amides, such as, PDMAT [Ta(NMe₂)₅], and PEMAT [Ta(NEtMe)₅] and Ta imides, such as, TBTDET [t-BuN═Ta(NEt₂)₃], and TAIMATA [t-AmN═Ta(NMe₂)₃] represent some currently available TaN precursors. Thermal stability of amides is problematic. For example, PDMAT is a solid with a melting point of 167° C. However, PDMAT decomposes at temperatures above 80° C. PEMAT is a low melting point solid. PEMAT also decomposes at temperatures above 80° C.

There is a continuing need in the art for tantalum precursors useful for deposition applications, e.g., to form copper migration barrier structures.

In current practice, copper migration barrier structures are formed by reactive sputter deposition of a TaN layer onto a patterned, nominally dense dielectric, followed by sputter deposition of Ta metal prior to sputter deposition of a copper seed layer.

There is correspondingly a need for barrier layers, e.g., for copper metallization of semiconductor device structures, that do not introduce nitrogen to the underlying dielectric film.

SUMMARY OF THE INVENTION

Aspects of various embodiments of the present invention relate generally to precursor compositions for forming tantalum-containing films, as well as to the tantalum-containing films, such as may be employed as barrier layers in semiconductor devices utilizing copper metallization, as well as to semiconductor device structures including tantalum-containing films.

In one aspect, an embodiment of the present invention relates to a tantalum compound of Formula I:

wherein: R¹, R², R³ and R⁴ can be the same as or different from one another, and each is independently selected from the group consisting of hydrocarbyl, alkyl, silyl, and, alkylamino.

In some embodiments, in Formula I, R¹ and R² cannot both be isopropyl at the same time and/or R¹ and R² cannot both be cyclohexyl at the same time.

One or more embodiments of the invention in another aspect relate to a tantalum precursor formulation, including a tantalum compound (Formulae I) as described above, in a solvent medium.

An example of a suitable solvent medium is an organic solvent, including but not limited to, hydrocarbon solvents such as pentane, hexane, heptane, octane, decane, THF, ether (e.g., dimethylether (DME)) and aromatic solvents such as toluene.

Other suitable solvents may be used.

In a further aspect, embodiments of the invention relate to a method of synthesizing a tantalum compound (Formula I) as described above, in which the method includes conducting synthesis according to Scheme 1 or Scheme 1a below:

where M=Ta.

A still further aspect of embodiments of the invention relate to a method of forming a tantalum-containing material on a substrate, including volatilizing a tantalum compound of Formula I as described above, to form a precursor vapor, and depositing tantalum on the substrate from the precursor vapor under deposition conditions therefor.

It is to be appreciated, however, that (according to one or more embodiments of the invention) the tantalum-containing material on a substrate, the tantalum-containing barrier layer on a substrate, or devices containing same, or methods for making the same, may involve (in whole, or in part) the tantalum compounds of Formula I.

In another aspect, one or more embodiments of the present invention relate to a semiconductor device structure, including a dielectric layer, a barrier layer overlying (or, for example, directly on) the dielectric layer, and a copper metallization overlying (or, for example, directly on) the barrier layer, wherein the barrier layer is optionally amorphous. See, for example, FIG. 5 hereof.

A still further aspect of one or more embodiments of the invention relates to a method of forming a Ta-containing barrier layer on a dielectric layer which, in turn, is on a substrate. The Ta-containing barrier layer may be formed by a process including CVD or ALD using precursors of Formula I as described herein. According to one embodiment of the present invention, the CVD or ALD is conducted at a temperature below about 400° C., in a reducing atmosphere.

Yet another aspect of one or more embodiments of the invention relates to a method of inhibiting copper migration in a structure including copper and material adversely affected by copper migration (and/or improving poor adhesion between the copper layer and the barrier layer underneath), comprising interposing a Ta-containing barrier layer between said copper and such material using precursors of Formula I as described herein. According to one embodiment of the present invention, the CVD or ALD is conducted at a temperature below about 400° C., in a reducing atmosphere (e.g., a suitable nitriding atmosphere such as NH₃—for example—ammonia gas or ammonia plasma).

Additional aspects of one or more embodiments of the present invention relate to making a semiconductor device, comprising forming a migration barrier by a vapor deposition process using a vapor deposition precursor including a tantalum compound (Formula I) as described herein, and semiconductor manufacturing methods including use of a tantalum compounds of such type.

The metal source precursors of the invention are volatile and thermally stable, and are usefully employed as precursors for CVD, ALD and/or digital CVD (sometimes referred to as rapid vapor deposition, or RVD) under reduced pressure deposition conditions in corresponding CVD, ALD or digital CVD reactors. In digital CDV, as in ALD, the substrate is sequentially exposed precursors in gaseous form. In digital CDV the process is repeated until a substrate coated with multiple layers reaches a desired thickness. The resulting coated substrate has a high conformality. Digital CVD differs from ALD in that the layers in digital CVD can be deposited more quickly.

The compositions of the present invention can be delivered to the CVD, ALD or digital CVD reactors in a variety of ways. For example, a liquid delivery system may be utilized, with the solid precursor(s) being dissolved in organic solvents, and liquid delivery processes being used to meter the solution into a vaporizer for transport of the vapor to the reactor. Alternatively, a combined liquid delivery and flash vaporization process unit may be employed, to enable low volatility materials to be volumetrically delivered, so that reproducible transport and deposition are achieved without thermal decomposition of the precursor, in order to provide a commercially acceptable CVD, ALD or digital CVD process. In still another alternative, a liquid delivery system may be utilized wherein the precursor is stored in and delivered from an ionic liquid.

In liquid delivery formulations, metal source precursors that are liquids may be used in neat liquid form, or liquid or solid metal source precursors may be employed in solvent formulations containing same. Thus, metal source precursor formulations of the invention may include solvent component(s) of suitable character as may be desirable and advantageous in a given end use application to form metals on a substrate.

Suitable solvents may for example include alkane solvents (e.g., hexane, heptane, octane, nonane, decane and pentane), aryl solvents (e.g., benzene or toluene), amines (e.g., triethylamine, tert-butylamine), imines and carbodiimides (e.g., N,N′-diisopropylcarbodiimide). The utility of specific solvent compositions for particular metal source precursors may be readily empirically determined, to select an appropriate single component or multiple component solvent medium for the liquid delivery vaporization and transport of the specific metal source precursor that is employed. In some embodiments, oxygenated species such as alcohols, ethers, ketones, aldehydes, and other species that might serve as coordinating species, can be employed.

In specific embodiments, the solvent utilized in the source reagent solutions of the invention are selected from among aliphatic hydrocarbons, aromatic hydrocarbons, ethers, esters, nitriles, and alcohols. The solvent component of the solution can comprise a solvent selected from the group consisting of: glyme solvents having from 1 to 20 ethoxy —(C₂H₄O)— repeat units; C₂-C₁₂ alkanols, organic ethers selected from the group consisting of dialkyl ethers comprising C₁-C₆ alkyl moieties, C₄-C₈ cyclic ethers; C₁₂-C₆₀-crown-O₄—O₂₀ ethers wherein the prefixed C_(i) range is the number i of carbon atoms in the ether compound and the suffixed O_(i) range is the number i of oxygen atoms in the ether compound; C₆-C₁₂ aliphatic hydrocarbons; C₆-C₁₈ aromatic hydrocarbons; organic esters; organic amines; and polyamines.

In another aspect of the invention, a solid delivery system may be utilized, for example, using the ProE-Vap® solid delivery and vaporizer unit (commercially available from ATMI, Inc., Danbury, Conn., USA).

In another aspect of the invention, a liquid delivery system may be utilized, for example using the NOWTrak® system (commercially available from ATMI, Inc., Danbury, Conn., USA). In still another aspect of the invention, the packaging utilized in liquid delivery employing the NOWTrak® system includes a disposable liner adapted to hold the liquid precursor composition. Exemplary systems include, but are not limited to, those set forth in U.S. Pat. No. 6,879,876, filed Jun. 13, 2001 and issued Apr. 12, 2005 and titled “Liquid handling system with electronic information storage”; U.S. patent application Ser. No. 10/139,104, filed May 3, 2002 and titled “Liquid handling system with electronic information storage”; U.S. patent application Ser. No. 10/742,125, filed Dec. 19, 2003 and titled “Secure Reader System”; and U.S. Provisional Patent Application No. 60/819,681 filed Jul. 10, 2006 entitled “Fluid storage vessel management systems and methods employing electronic information storage,” all of which are hereby incorporated by reference in their entirety.

Other non-limiting aspects, features and advantages of the present invention will be more fully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 includes the ¹H & ¹³C NMRs of [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄]. The top plot is the ¹³C NMR. The bottom plot is the ¹H NMR.

FIG. 2 is an STA (simultaneous thermal analysis) diagram illustrating comparison of STA data among DEMAT (5.15 mg), [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄] (9.56 mg) and (NMe₂)₄Ta(ηPr^(i)NC(NMe₂)NPr^(i)) (10.57 mg).

FIG. 3 is an ORTEP diagram of [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄].

FIG. 4 is a packing diagram of [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄] along the c axis.

FIG. 5 is a schematic illustration of a semiconductor device structure according to one embodiment of the present invention, featuring an amorphous Ta-containing barrier film and copper metallization.

DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS THEREOF

One or more embodiments of the present invention relate in various aspects to precursor compositions (and vapor, gas or plasma forms thereof) useful for forming tantalum-containing films (e.g., barrier layers or films). Other embodiments relate to tantalum-containing films, such as may be employed as barrier layers in semiconductor devices utilizing copper metallization, as well as to other semiconductor device structures including tantalum-containing films.

As used herein, the term “semiconductor device structures” is intended to be broadly construed to include microelectronic devices, products, components, assemblies and subassemblies that include a semiconductor material as a functional material therein. Illustrative examples of semiconductor device structures include, without limitation, resist-coated semiconductor substrates, flat-panel displays, thin-film recording heads, microelectromechanical systems (MEMS), and other advanced microelectronic components. The semiconductor device structure may include patterned and/or blanketed silicon wafers, flat-panel display substrates or fluoropolymer substrates. Further, the semiconductor device structure may include mesoporous or microporous inorganic solids.

“Alkyls” as used herein include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, s-butyl, t-butyl, pentyl and isopentyl and the like. “Aryls” as used herein includes hydrocarbons derived from benzene or a benzene derivative that are unsaturated aromatic carbocyclic groups of from 6 to 10 carbon atoms. The aryls may have a single or multiple rings. The term “aryl” as used herein also includes substituted aryls. Examples include, but are not limited to phenyl, naphthyl, xylene, phenylethane, substituted phenyl, substituted naphthyl, substituted xylene, substituted phenylethane and the like. “Cycloalkyls” as used herein include, but are not limited to cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like. In all chemical formulae herein, a range of carbon numbers will be regarded as specifying a sequence of consecutive alternative carbon-containing moieties, including all moieties containing numbers of carbon atoms intermediate the endpoint values of carbon number in the specific range as well as moieties containing numbers of carbon atoms equal to an endpoint value of the specific range, e.g., C₁-C₆, is inclusive of C₁, C₂, C₃, C₄, C₅ and C₆, and each of such broader ranges may be further limitingly specified with reference to carbon numbers within such ranges, as sub-ranges thereof. Thus, for example, the range C₁-C₆ would be inclusive of and can be further limited by specification of sub-ranges such as C₁-C₃, C₁-C₄, C₂-C₆, C₄-C₆, etc. within the scope of the broader range.

As used herein, the term “film” refers to a layer of deposited material having a thickness below 1000 micrometers, e.g., from such value down to atomic monolayer thickness values. In various embodiments, film thicknesses of deposited material layers in the practice of the invention may for example be below 100, 10, or 1 micrometers, or in various thin film regimes below 200, 100, or 50 nanometers, depending on the specific application involved. As used herein, the term “thin film” means a layer of a material having a thickness below 1 micrometer.

It is noted that as used herein and in the appended claims, the singular forms “a”, “and”, and “the” include plural referents unless the context clearly dictates otherwise.

The invention, as variously described herein in respect of features, aspects and embodiments thereof, may in particular implementations be constituted as comprising, consisting, or consisting essentially of, some or all of such features, aspects and embodiments, as well as elements and components thereof being aggregated to constitute various further implementations of the invention.

One or more embodiments of the present invention relate to a class of precursors selected from among precursors of Formula I below:

wherein: R¹, R², R³ and R⁴ can be the same as or different from one another, and each is independently selected from the group consisting of hydrocarbyl, alkyl, silyl, and alkylamino. In some embodiments, R¹ and R² cannot both be isopropyl at the same time and/or R¹ and R² cannot both be cyclohexyl at the same time.

Additionally, according to one or more embodiments of the present invention, R¹, R², R³ and R⁴ can be the same as or different from one another, and each is independently selected from hydrocarbyl (e.g., C₁-C₁₂ alkyl such as C₁ alkyl (i.e., methyl), C₂ alkyl (i.e., ethyl), C₃ alkyl (e.g., n-propyl or iso-propyl), C₄ alkyl (e.g., n-butyl, iso-butyl, t-butyl), C₅ alkyl (e.g., n-pentyl, iso-pentyl), C₈ alkyl (e.g., octyl), C₉ alkyl (e.g., nonyl), C₁₀ alkyl, C₁₁ alkyl, C₁₂ alkyl), alkenyl (e.g., C₁-C₁₂ alkenyl), and aryl and any combination or sub-combination thereof), hydrogen, silyl, hydrazyl (for example Me₂NNH—) and alkylamino (for example Me₂N—, MeHN—, etc.).

As used herein, the designation of organo substituents by reference to carbon numbers, includes ranges as well as sub-ranges within the ranges identified by end-point carbon numbers, and such sub-ranges may be specified, e.g., as including one of such end-point carbon numbers in such a sub-range, or as including carbon numbers greater than the lower end-point carbon number and less than the upper end-point carbon number of the range, to constitute various sub-ranges in the various specific embodiments of the invention. Alkyl groups may be branched or unbranched.

The precursors of Formula I (described herein) are useful for forming tantalum-containing films, e.g., involving CVD and ALD of tantalum nitride and Ta metal films. These precursors also have utility as low temperature deposition precursors for forming Ta₂O₅ and other Ta oxide films, e.g., in the fabrication of capacitors such as back-end capacitors.

These novel complexes may be readily purified, and their solution behavior in solvent media employed for liquid delivery processes, e.g., for CVD or ALD of Ta, TaN or Ta₂O₅ films is superior to that of PDMAT [Ta(NMe₂)₅], PEMAT [Ta(NEtMe)₅], etc.

The precursors of Formula I may be usefully employed for deposition of Ta-containing material on substrates, including, without limitation, deposition of Ta, TaN, Ta₂O₅, TaSiN, BiTaO₄, etc. The Ta-containing material may be deposited on the substrate in any suitable manner, with deposition processes such as CVD and ALD sometimes being preferred. Depending on the substituents employed, the Formula I precursors may also be deposited by solid delivery techniques, e.g., in which the precursor is volatilized from a solid form under suitable temperature and pressure, e.g., vacuum conditions.

The CVD process may be carried out in any suitable manner, for example, with the volatilized precursor being conveyed to a CVD reactor for contact with a heated substrate, e.g., a silicon wafer-based structure, or other microelectronic device substrate. In such process, the volatilized precursor may be directed to the CVD reactor in neat form, or, more typically, in a carrier gas stream, which may include inert gas, plasma, oxidant, reductant, co-deposition species, and/or the like.

The CVD process may be carried out by liquid delivery processing, for example, in which the Ta precursor is dissolved or suspended in a solvent medium, which may include a single solvent or multi-solvent composition, as appropriate to the specific deposition application involved. Suitable solvents for such purpose include any compatible solvents that are consistent with liquid delivery processing, as for example, hydrocarbon solvents, etc., with a suitable solvent for the specific deposition application being readily determinable within the skill of the art based on the disclosure herein.

The precursors of Formula I have particular utility as CVD or ALD precursors for deposition of thin films of TaN and TaSiN as barriers in integrated circuits, e.g., integrated circuitry including dielectric material and copper metallization.

The precursors of Formula I, and Formula II (i.e., M(NR³R⁴)₅; M=Ta or as described herein; R³ and R⁴ are as described herein) also may have particular utility as CVD or ALD precursors for low temperature deposition of thin films of high k capacitor materials such as Ta₂O₅ and BiTaO₄.

The precursors of Formula I may also have particular utility as CVD or ALD precursors for deposition of Ta containing metal films as barriers in integrated circuits.

Various embodiments of the present invention include a class of precursors selected from among precursors of Formula I described above. Additionally, according to one or more embodiments of the present invention, R¹, R², R³ and R⁴ can be the same as or different from one another, and each is independently selected from hydrocarbyl substituents including alkyl, arylalkyl, alkaryl, alkenyl, alkenylaryl, arylalkenyl, allyl, hydrogen, silyl, hydrazyl (for example, Me₂NNH—) and alkylamino (for example, Me₂N—, MeHN—, etc.) etc. that are optionally further substituted with one or more heteroatoms such as N, S, and O and/or with halo substituents and any combination or sub-combination thereof, and providing functionality that is sterically and chemically appropriate to the use of the composition as a precursor for forming tantalum-containing films and materials—as described herein.

The precursors of Formula I have utility for CVD and ALD of Ta carbide and Ta metal films, as well as for low temperature deposition of TaN, Ta₂O₅ and other Ta-related oxide films for use in capacitor fabrication.

The precursors of Formula I can be synthesized by Scheme 1 or Scheme 1a below:

In such synthetic schemes, R¹, R², R³, and R⁴ are as described herein and M is tantalum.

The Formula I precursors are thermally stable and stable in solution. The R¹, R², R³, and R⁴ ligands may be appropriately selected for the specific deposition application employed, e.g., for CVD or ALD deposition processing to form the desired Ta-containing material on the deposition substrate, within the skill of the art—based on the disclosure herein. The Formula I precursors are readily purified, and their solution behavior in solvent media may be suitably employed for liquid delivery processes, e.g., for CVD or ALD of Ta, TaN or Ta₂O₅ films.

The precursors of Formula I have utility as CVD or ALD precursors for deposition of thin films of TaN and TaSiN as barriers in integrated circuits, e.g., integrated circuitry including dielectric material and copper metallization.

The precursors of Formula I also have particular utility as CVD or ALD precursors for low temperature deposition of thin films of high k capacitor materials such as Ta₂O₅ and BiTaO₄.

The precursors of Formula I have utility for CVD and ALD of Ta nitride and Ta metal films, as well as for low temperature deposition of Ta₂O₅ and other Ta-related oxide films for use in capacitor fabrication.

FIG. 1 shows a ¹³C and ¹H NMR plot of. [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄]. The top plot is the ¹³C NMR. The bottom plot is the ¹H NMR.

FIG. 2 is an STA (simultaneous thermal analysis) diagram illustrating comparison of STA data among DEMAT (green line, 5.15 mg), [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄] (blue line, 9.56 mg) and (NMe₂)₄Ta(η2-Pr^(i)NC(NMe₂)NPr^(i)) (brown line, 10.57 mg). Thermal analysis (see STA data in FIG. 2) showed the material transport completely below 250° C. with a low residue of 1.6% at 800° C. Notably the introduction of the asymmetric chelate ligand in [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄] dropped the T₅₀ by 21° C. as compared to that of [(Pr^(i)NC(NMe₂)NPr^(i))Ta(NMe₂)₄], which made it very comparable to DEMAT.

FIG. 3 is an ORTEP diagram of [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄]

FIG. 4 is a packing diagram of [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄] along the c axis.

FIG. 5 is a schematic illustration of a semiconductor device structure according to one embodiment of the present invention, featuring an amorphous Ta-containing barrier film and copper metallization.

As noted, the precursors of Formula I may be usefully employed for deposition of Ta-containing material on substrates, including, without limitation, deposition of Ta, TaN, Ta₂O₅, TaSiN, BiTaO₄, etc. The Ta-containing material may be deposited on the substrate in any suitable manner, for example, with deposition processes such as CVD and ALD sometimes being preferred. Depending on the substituents employed, the Formula I precursors may also be deposited by solid delivery techniques, e.g., in which the precursor is volatilized from a solid form under suitable temperature and pressure, e.g., vacuum conditions.

The CVD process may be carried out in any suitable manner, with the volatilized precursor being conveyed to a CVD reactor for contact with a heated substrate, e.g., a silicon wafer-based structure, or other microelectronic device substrate. In such process, the volatilized precursor may be directed to the CVD reactor in neat form, or, more typically, in a carrier gas stream, which may include inert gas, plasma, oxidant, reductant, co-deposition species, or the like.

Although the choice of specific process conditions for CVD is readily made by the skilled artisan based on the disclosure herein, it may be suitable in some applications to conduct chemical vapor deposition at process conditions including a deposition temperature range from about 600 to about 900K and a deposition pressure range from about 0 to about 100 Pascal.

The CVD process may be carried out by liquid delivery processing, in which the Ta precursor is dissolved or suspended in a solvent medium, which may include a single solvent or multi-solvent composition, as appropriate to the specific deposition application involved. Suitable solvents for such purpose include any compatible solvents that are consistent with liquid delivery processing, as for example, hydrocarbon solvents, etc., with a suitable solvent for a specific deposition application being readily determinable within the skill of the art based on the disclosure herein. Examples of suitable hydrocarbon solvents include, but are not limited to, pentane, hexane, heptane, octane, decane, cyclohexane, THF, toluene, and DME. Other suitable solvents may be used.

The precursors of Formula I may have particular utility as CVD or ALD precursors for deposition of thin films of TaN and TaSiN as barriers in integrated circuits, e.g., integrated circuitry including dielectric material and copper metallization.

The precursors of Formula I may also have particular utility as CVD or ALD precursors for low temperature deposition of thin films of high k capacitor materials such as Ta₂O₅ and BiTaO₄.

The precursors of Formula I may also have particular utility as CVD or ALD precursors for deposition of Ta metal films as barriers in integrated circuits.

One or more embodiments of the present invention relate to tantalum-containing barrier films, such as may usefully be employed as diffusion barriers in semiconductor devices featuring copper metallization, and reflects the discovery that Ta compounds (Formula I) can be used to efficiently form tantalum-based barrier films at low temperatures under reducing conditions.

The Ta compounds that can be usefully employed for forming the Ta-containing barrier film may be of any suitable type, including a Ta—NR¹—C(NR³R⁴)—NR² (see Formula I and Formula II noted herein containing same) moiety and substituents that permit the Ta-containing barrier film to be formed (in whole or in part)—sometimes preferably as an amorphous structure.

In use, the Ta compound precursor may be volatilized to form a precursor vapor for CVD or ALD formation of the Ta-containing barrier film. The precursor volatilization and delivery to the deposition chamber may be carried out in any suitable manner, e.g., by bubbler delivery involving an inert or reducing carrier gas flow through the bubbler, or by solid delivery technique, in which the precursor is volatilized from a solid form under suitable temperature and pressure, e.g., vacuum conditions involving sublimation of the precursor compound and mixing of the precursor vapor with inert or reducing carrier gas, or by liquid delivery technique in which the precursor is dissolved in a suitable solvent medium, such as hexane, octane, toluene or other organic solvent, with the resulting liquid being flash vaporized to produce the precursor vapor, or by any other appropriate technique that results in the provision of a precursor vapor suitable for contacting with the substrate (the layer to be coated).

The precursor vapor can contain or be mixed with a reducing agent of appropriate character and concentration to provide a suitable reducing atmosphere in the deposition chamber. In the deposition chamber, the substrate on which the barrier film is to be formed, is heated to temperature effective for contacting with the precursor vapor to affect the film formation process, and then contacted with the precursor vapor to form the Ta-containing barrier film on the substrate.

The reducing agent can be hydrogen, hydrogen plasma, remote hydrogen plasma, silane, disilane, borane, diborane, ammonia (gas or plasma), amines (Me₂NH, t-BuNH₂, Et₂NH) or the like, or mixture of two or more of the foregoing species, as satisfactory to provide an atmosphere in the deposition chamber that facilitates the formation of the Ta-containing film. The reducing co-reactants may be introduced simultaneously with the Ta precursor or in an alternating manner (i.e., via digital or pulsed CVD or ALD).

The substrate can be of any appropriate type. In one embodiment, the substrate includes a silicon wafer having a low k dielectric film thereon, suitably patterned for the deposition of the barrier film to accommodate subsequent copper metallization of the semiconductor device structure formed on the wafer.

The deposition may be carried out at temperature to form the Ta-containing barrier layer that is appropriate for the specific technique that is employed for the deposition, e.g., CVD, ALD, digital CVD, pulsed CVD, or the like. In general, temperature of 100° C. or higher, but below 400° C., can be utilized as the deposition temperature.

In some embodiments, the temperature for deposition is below 390° C., and specific operating regimes for the process include temperatures in a range of from about 250° C. to about 380° C., and temperatures in a range of from about 275° C. to about 350° C. in other embodiments of the invention. ALD may for example be carried out at a temperature of about 280° C.

It is to be appreciated that the foregoing values without “about” preceding the specific values are encompassed by this disclosure.

Pressure may likewise be selected based on volatilization, transport and deposition properties of the specific precursor employed, with vacuum pressures being useful in some applications, e.g., where solid delivery is employed as the delivery technique. CVD and ALD pressures may include deposition pressures in a range of from about 0 to about 1000 Pascal, or other pressure appropriate to the particular deposition methodology.

[(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄] is a particularly suitable precursor for low temperature deposition applications for formation of Ta-containing films on substrates.

FIG. 5 is a schematic illustration of a semiconductor device structure 10 according to one embodiment of the present invention, featuring an amorphous Ta-containing barrier film and copper metallization.

The device structure 10 includes a silicon substrate 12, on which has been deposited a low k dielectric material 14. An amorphous barrier film 16 is deposited on the dielectric in accordance with an embodiment of the invention, and overlaid with a seed layer 18 of copper or ruthenium, on which is deposited a copper metallization layer 20. The barrier film (e.g., Ta-containing film or layer) may be of any suitable thickness, e.g., from about 10 Angstroms to about 1000 Angstroms, or greater, depending on the nature of the dielectric and the overall processing scheme including process temperature in the other fabrication steps of the device manufacturing operation.

In an alternative embodiment, the seed layer may be composed of ruthenium or other suitable seed for deposition of copper metallization.

Thus, a precursor compound of Formula I may be used to efficiently and cost-effectively deposit a tantalum-containing film in a reducing atmosphere at low temperature, to produce an amorphous Ta-containing barrier against copper diffusion, in semiconductor device structures featuring copper metallization. The invention thereby achieves a significant advance in the art of copper metallization using thermally stable Ta-containing precursors to form corresponding barrier layers in the device structure.

The R group substituents of tantalum compounds of Formula I hereof can further include variations and derivatives of the chemical moieties specifically identified herein, e.g., in respect of hydrocarbyl substituents including alkyl, arylalkyl, alkaryl, alkenyl, alkenylaryl, arylalkenyl, allyl, hydrogen, silyl, hydrazyl (for example, Me₂NH—) and alkylamino (for example, Me₂N—, MeHN—, etc.) etc. that are optionally further substituted with heteroatoms such as N, S, and O and/or with halo substituents, providing functionality that is sterically and chemically appropriate to the use of the tantalum composition as a precursor for forming tantalum-containing films and materials.

The tantalum compositions of the invention can be utilized in solution including any suitable solvents, such as for example hydrocarbon solvents (pentane, hexane, heptane, octane, decane, cyclohexane, etc.), THF, ethers (e.g., DME), toluene and the like, as necessary or desirable in a given application of a specific tantalum composition of the invention.

The following example is non-limiting and provided for illustration only.

Example 1 Synthesis of [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄]

To a 250 mL flask filled with 1.16 g (9.19 mol) 1-tert-Butyl-3-ethylcarbodiimide (Bu^(t)N═C═NEt) and 100 mL hexane, 3.73 g (9.29 mmol) of PDMAT (Ta(NMe₂)₅), was added at 0° C. The green-yellow reaction mixture was stirred and warmed up during overnight. All the volatiles were then removed under vacuum.

The resulting bright yellow solid was sublimed under vacuum (100° C., 100 mTorr) and 3.4 g yellow solid [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄] (6.44 mol, 70% overall yield). Data for [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄]: ¹H NMR (benzene-d6, 21C): 1.19 (t, 3H, NCH₂CH₃), 1.38 (s, 9H, NC(CH₃)₃), 2.47 (s, 6H, CN(CH₃)₂), 3.25 (q, 2H, NCH₂CH₃), 3.41 (s, 12H, N(CH₃)₂), 3.49 (s, 6H, N(CH₃)₂) 3.52 (s, 6H, N(CH₃)₂), 13C{1H} NMR (benzene-d6, 21C): 18.18 (NCH₂CH₃), 32.17 (NCH₂CH₃), 40.17 (NC(CH₃)₃), 42.19 (NC(CH₃)₃), 47.29 (N(CH₃)₂), 47.39 (N(CH₃)₂), 49.58 (N(CH₃)₂), 53.13 (CN(CH₃)₂), 168.55 (CN(CH₃)₂). See FIG. 1. Anal. Calcd for TaC₁₇H₄₄N₇: C, 38.71%; H, 8.41%; N, 18.59%. Found: C, 38.55%; H, 8.50%; N, 18.26%.

Although the invention has been described herein with reference to non-limiting illustrative features, aspects and embodiments, it will be appreciated that the invention may be practiced with modifications, variations and in other embodiments, as will suggest themselves to those of ordinary skill based on the disclosure herein. The invention therefore is to be interpreted and construed, as encompassing all such modifications, variations, and other embodiments, within the spirit and scope of the claims hereafter set forth. 

1. A method for making a tantalum compound of Formula I:

wherein: R¹, R², R³ and R⁴ can be the same as or different from one another, and each is independently selected from the group consisting of hydrogen, hydrocarbyl, alkyl, silyl, alkylamino, alkenyl, aryl and hydrazyl, with the provisos that R¹=R²≠iso-propyl, and R¹=R²≠cyclohexyl; wherein said R¹, R², R³ and R⁴ may be optionally further substituted with a N, S, O, or a halogen atom, said method comprising the step of: (a) reacting a compound of Formula II below: M(NR³R⁴)₅  (Formula II),  with a compound of Formula III: R¹N═C═NR²  (Formula III),  wherein M is tantalum and R¹, R², R³ and R⁴ are as indicated above.
 2. The method of claim 1, having one or more compatible characteristics selected from the group consisting of: (i) said reacting step (a) being conducted in an organic solvent and said compound of Formula III being added to said compound of Formula II in said organic solvent; (ii) said reacting step (a) being conducted in an organic solvent selected from the group consisting of pentane, hexane, heptane, octane, decane, cyclohexane, THF, toluene, and DME; (iii) said reacting step (a) being conducted in a temperature range from about 0° C. to about 200° C.; (iv) said reacting step (a) being conducted in a temperature range from about 0° C. to about 150° C.; (v) said reacting step (a) being conducted in a temperature range from about 0° C. to about 100° C.; (vi) said reacting step (a) being conducted in a temperature range from about 0° C. to about 75° C.; (vii) said reacting step (a) being conducted in a temperature range from about 0° C. to about 50° C.; (viii) said reacting step (a) being conducted in a temperature range from about 0° C. to about 30° C.; (ix) said alkyl being a C₁-C₁₂ alkyl selected from the group consisting of C₁ alkyl, C₂ alkyl, C₃ alkyl, C₄ alkyl, C₅ alkyl, C₆ alkyl, C₇ alkyl, C₈ alkyl, C₉ alkyl, C₁₀ alkyl, C₁₁ alkyl or C₁₂ alkyl; (x) said alkyl being a C₁-C₄ alkyl selected from the group consisting of C₁ alkyl, C₂ alkyl, C₃ alkyl and C₄ alkyl; (xi) said alkyl being methyl, ethyl, n-propyl, i-propyl, n-butyl, or t-butyl; (xii) said R¹ and R² being the same and said R³ and R⁴ being the same but said R¹ and R² not being the same as said R³ and R⁴; (xiii) said R¹ and R² not being the same but said R³ and R⁴ being the same; (xiv) said R¹ and R² being the same but said R³ and R⁴ not being the same; (xv) said R¹, R², R³ and R⁴ being the same; (xvi) none of R¹, R², R³ and R⁴ being the same; and (xvii) some of said R¹, R², R³ and R⁴ being the same.
 3. The method of claim 1, wherein said reacting step (a) is conducted in a hydrocarbon solvent.
 4. The method of claim 3, wherein said hydrocarbon solvent is selected from the group consisting of pentane, hexane, heptane, octane, decane, cyclohexane, THF, toluene, and ethers.
 5. The method of claim 3, wherein said hydrocarbon solvent is selected from the group consisting of pentane, heptane, octane, decane, cyclohexane, THF, toluene, and ethers.
 6. The method of claim 1, wherein said reacting step (a) is conducted in dimethylether (DME).
 7. The method of claim 1, wherein each of R¹, R², R³ and R⁴ is independently selected from the group consisting of hydrocarbyl, alkyl, silyl, and alkylamino.
 8. The method of claim 1, wherein each of R¹, R², R³ and R⁴ is independently selected from the group consisting of alkyl, arylalkyl, alkaryl, alkenyl, alkenylaryl, arylalkenyl, allyl, hydrogen, silyl, hydrazyl, and alkylamino.
 9. The method of claim 1, wherein said tantalum compound is (Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄.
 10. The method of claim 1, wherein the tantalum compound includes asymmetric chelate ligands R¹ and R².
 11. The method of claim 10, wherein both chelate ligands R¹ and R² are alkyl ligands.
 12. The method of claim 11, wherein one of said chelate ligands R¹ and R² is ethyl.
 13. The method of claim 11, wherein one of said chelate ligands R¹ and R² is t-butyl.
 14. The method of claim 11, wherein the tantalum compound displays simultaneous thermal analysis (STA) behavior including complete material transport below 250° C.
 15. The method of claim 10, wherein R³=R⁴=methyl.
 16. A method of making [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄], comprising reacting Bu^(t)N═C═Net and Ta(NMe₂)₅ in a reaction medium comprising solvent, and recovering said [(Bu^(t)NC(NMe₂)NEt)Ta(NMe₂)₄] under vacuum from said reaction medium.
 17. The method of claim 16, wherein said solvent comprises a hydrocarbon solvent.
 18. The method of claim 17, wherein said hydrocarbon solvent is selected from the group consisting of pentane, hexane, heptane, octane, decane, cyclohexane, THF, toluene, and ethers.
 19. The method of claim 17, wherein said hydrocarbon solvent is selected from the group consisting of pentane, heptane, octane, decane, cyclohexane, THF, toluene, and ethers.
 20. The method of claim 16, wherein said solvent comprises hexane. 